Phase-locked loop systems and methods
AssigneeLattice Semiconductor Corporation
InventorsHarald Weller, Ludmil Nikolov, Ji Zhao
Life of this patent
Estimating the term…
Abstract
Improved common mode feedback techniques are provided for charge pumps, phase-locked loops (PLLs), and other circuits. For example, in accordance with an embodiment of the present invention, a circuit includes a loop filter having first and second loop filter nodes. An amplifier is provided having first and second differential inputs respectively coupled to the first and second loop filter nodes. A first current source is coupled to the first loop filter node and a second current source is coupled to the second loop filter node. The first and second current sources are adapted to continuously adjust a common mode voltage of the loop filter nodes.
Claims20
A circuit comprising:
- a loop filter having first and second loop filter nodes;
- an amplifier having first and second differential inputs respectively coupled to the first and second loop filter nodes;
- a first current source coupled to the first loop filter node;
- and
- a second current source coupled to the second loop filter node, wherein the first and second current sources are adapted to continuously adjust a common mode voltage of the loop filter nodes.
A method of correcting a common mode voltage, the method comprising:
- receiving a plurality of control signals responsive to a phase relationship between a reference signal and a feedback signal;
- coupling first and second loop filter nodes of a loop filter to first and second current sources in response to the control signals;
- and
- correcting a common mode voltage of the loop filter nodes independent of the control signals.
A circuit comprising:
- a loop filter having first and second loop filter nodes;
- means for selectively coupling current sources to the loop filter nodes in response to control signals;
- and
- means for correcting a common mode voltage of the loop filter nodes independent of the control signals.
Dependencies are inferred from the claim text.